1. Field of the Invention
The present invention is directed to a hydrodynamic clutch device, especially a hydrodynamic torque converter, with a housing containing a fluid chamber. The fluid chamber is divided into a first fluid chamber containing a turbine wheel and impeller wheel and a second fluid chamber by means of a piston of a lockup clutch, which piston is movable axially with respect to a housing axis.
2. Discussion of the Prior Art
A hydrodynamic torque converter of the type mentioned above is known, for example, from U.S. Pat. No. 4,143,561. In the known torque converter, the piston is rotatable relative to the housing and is connected via a torsional vibration damping arrangement with a hub of the turbine wheel so as to transmit torque.
Another hydrodynamic torque converter of the type mentioned above is known from French reference FR 2 341 791. As far as can be gathered from FIG. 1 of this laid open application, the piston is arranged at the housing so as to be fixed with respect to rotation relative to it and engages by its inner circumference in a sealing engagement in the outer circumference of a housing hub by means of a radial inner sealing ring and engages in a sealing engagement by its outer circumference in an inner circumference of a housing wall by means of a radial outer sealing ring, so that the first fluid chamber area and the second fluid chamber area are sealed relative to one another regardless of the state (lockup state, or non-lockup state) of the lockup clutch. A higher fluid pressure can be applied to the second fluid chamber area via a bore hole in a driven shaft of the converter relative to a fluid pressure in the first fluid chamber area in order to put the lockup clutch into the lockup state, that is, to engage the lockup clutch. The first fluid chamber area is connected to a fluid pump (oil pump) via an annular fluid passage which is formed between a supporting shaft of a stator wheel of the converter, which supporting shaft is foxed as a hollow shaft, and a housing hub. Since the second fluid chamber area is sealed relative to the first fluid chamber area, the first fluid chamber area must be additionally connected to another fluid passage in order to provide a fluid circuit through the first fluid chamber area, which is a compulsory requirement for discharging friction heat from the first fluid chamber area. It is not clear from the Figure, which may not be entirely correct in some details, whether or not the additional fluid passage to which the first fluid chamber area must be connected runs between the outer circumference of the driven shaft and the inner circumference of the supporting shaft as is generally the case in other known torque converters.
It is an object of the present invention to provide a hydrodynamic clutch device which has an economically producible piston and which can be controlled in a simple manner and economically with respect to the construction of an associated fluid supply and/or control valve arrangement in relation to the engagement and disengagement of the lockup clutch and the exchange of fluid contained in the first fluid chamber area for the purpose of discharging heat.
This object is met through a hydrodynamic clutch device, especially a hydrodynamic torque converter of the type mentioned above, in which, according to the invention, the piston is connected to the housing so as to be fixed with respect to rotation relative to it. A fluid pressure which is higher than a fluid pressure in the first fluid chamber area can be applied to the second fluid chamber area in order to bring the lockup clutch into a lockup state. In a non-lockup state of the lockup clutch, the two fluid chamber areas are in a fluid flow connection and fluid can be supplied to the fluid chamber via the first fluid chamber area. When fluid is supplied to the first fluid chamber area fluid can be discharged from the fluid chamber exclusively via the second fluid chamber area.
According to the above, a two-line system is sufficient for controlling the clutch device, wherein a fluid source, especially a pressure fluid source, is connected to the two-line system, e.g., via a simple switching valve, either to the first fluid chamber area or to the second fluid chamber area and an associated fluid receptacle (for example, a reservoir, suction connection of a fluid pump, or the like) is connected to the other respective fluid chamber area.
When the fluid source is connected to the first fluid chamber area, the lockup clutch is put into the non-lockup state by a corresponding axial movement of the piston or is held in this non-lockup state and fresh (especially cooled) fluid flows out of the fluid source into the first fluid chamber area, from which fluid which is correspondingly xe2x80x9cusedxe2x80x9d (heated by friction) flows into the second fluid chamber area and then back into the fluid receptacle, so that there is established through the fluid chamber a fluid circuit through which friction heat can be reliably transported out of the fluid chamber. A closed fluid circuit preferably exists via a fluid cooler, so that the fluid withdrawn from the fluid chamber, more precisely, from the second fluid chamber area, is supplied again to the first fluid chamber area after cooling.
However, when the fluid source is connected to the second fluid chamber area by corresponding switching of the switching valve, the piston is moved axially in the direction of an engagement position by the fluid flowing into the second fluid chamber area and the lockup clutch is accordingly moved into the lockup state. Since, in the lockup state, the turbine wheel and impeller wheel and the fluid contained in the first fluid chamber area essentially rotate jointly about the housing axis, only a little friction is generated in the housing in this state, so that there is no need for an exchange of fluid for cooling. Consequently, the fluid flow connection can be interrupted in the lockup state. An interruption in the fluid flow connection in the lockup state has the advantage that correspondingly higher pressures can be built up in the second fluid chamber area and the lockup clutch can consequently transmit high torques. For this reason, it is preferred that the two fluid chamber areas are substantially sealed relative to one another in the lockup state.
In this regard, it is suggested that the fluid flow connection existing in the non-lockup state between the two fluid chamber areas leads through friction surface arrangements of the lockup clutch which are associated with one another and which are in a frictional and sealing engagement in the lockup state and consequently automatically interrupt the fluid flow connection.
A substantial advantage of the described construction is that a sealing ring arrangement provided at the piston on the radial outside and a respective sealing seat arrangement of the piston are not required, since the sealing is not effected in the lockup state by the friction surface arrangements. Obviously, in the non-lockup state, no sealing is required because in this state of the lockup clutch a fluid flow connection exists between both fluid chamber areas according to the invention.
The lockup clutch can comprise a plate arrangement and an abutment arrangement. This plate and abutment arrangement can have at least one driven-side plate in a torque-transmitting connection with a drive shaft and an abutment which is arranged at the housing so as to be fixed with respect to relative rotation. Further, there is provided at least one housing-side plate which is fixed with respect to relative rotation at the housing. In the event that there is only one driven-side plate, the arrangement is preferably carried out in such a way that the plate having a friction surface on both sides engages between a friction surface of the piston and a friction surface of the abutment. When a housing-side plate having a friction surface on both sides is provided, a first driven-side plate engages between the friction surface of the piston and the one friction surface of the housing-side plate and a second driven-side plate engages between the other friction surface of the housing-side plate and the friction surface of the abutment. For a greater quantity of plates, construction is carried out in a corresponding manner, wherein the quantity of driven-side plates exceeds the quantity of housing-side plates by one, so that every driven-side plate engages between two housing-side friction surfaces and consequently a housing-side friction surface and a driven-side friction surface lie opposite one another in pairs.
For fluid control of the clutch device, the first fluid chamber area is connected to an annular fluid passage between a housing hub and a supporting shaft of a stator wheel of the clutch device and/or is connected to an annular fluid passage between a/the driven shaft and the supporting shaft. When no supporting shaft is provided, for example, in the case of a hydrodynamic clutch device without a stator wheel, only an annular fluid passage which is constructed between the driven shaft and the housing hub is provided as a rule.
With respect to the second fluid chamber area, it is suggested that this second fluid chamber area is connected to a fluid passage formed in a/the driven shaft.
The fluid is generally a hydraulic liquid, especially hydraulic oil.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.